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Is it better for a flap and/or aileron to be an airfoil shape or simply replicating the trailing edge shape of the wing?
I am designing a UAV with the goals, broadly speaking, of a short take-off and high top-speed. I've already selected the airfoil for the wing itself. The wing is going to have a single slotted flap, no leading edge devices.
I was wondering if having the flap in the shape of an airfoil would provide better aerodynamic properties that would ultimately help achieve a shorter take-off. The alternative would be a flap that takes on the shape of the trailing edge and we be symmetric. I know it is common practice to go with the latter, but how do these compare?
Also, which shape would be better for the aileron?

If you already know your wing airfoil, don't you think you will get better answers when you let us know what it is?

For most control surfaces (including ailerons, elevators, rudder, etc), we use what is called a 'plain flap'.
A plain flap has a simple hinge (rotation only, no translation), with the axis of rotation within the airfoil -- typically centered vertically.  The aft portion of the plain flap maintains the shape of the airfoil, the leading side is usually rounded.
Importantly, the plain flap usually incorporates some sort of seal to prevent flow from going through the gap from the lower to upper side (or vis versa).
Most control surface applications prefer a plain flap because they can be deflected symmetrically -- with essentially equivalent effectiveness in both directions.
Things get more complex when you go to some sort of slotted flap -- a flap where flow intentionally goes through the gap.  In this case, it is important to aerodynamically design the cove and the entirety of the flap.  In this case, the flap(s) will be their own airfoil shape -- but you still want them to package together into a shape like the cruise airfoil.
Doing a proper high lift airfoil design is most likely beyond your capabilities and resources.  However, you should be able to look at existing systems applied to similar cruise airfoils and draw up something that is very representative.
NASA has a lot of reports available online that include high lift airfoils designed to various cruise airfoils.  I would start there.


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Why military parachute backpack stays with the aircraft?
As seen on this youtube video where military personnel jumps while the backpack stays attached to the aircraft, why is that? what is the purpose of it compared to the other non military skydiving parachute? And what is the name of this type of parachute system? And last but not least, is this type of parachute used in civilian world?
Thanks.

Related

Oh 'Static Line' that's how its called, thanks @CatchAsCatchCan

It requires a decent amount of skill and training to properly stabilize yourself in freefall. So for ease of training the military employs a static line for airdrops. In many air-drop situations you will be dropped too low to do much freefalling so an immediate release of the chute is required anyway.
With a static line the paratrooper won't need to know anything about which altitudes they should deploy the main parachute. Instead the procedure is jump, check if chute inflates properly, if not deploy reserve, if that fails panic and say your prayers.
The static line also helps the soldier orient themselves upright by the drag of the line and the canopy starts to inflate immediately as they clear the turbulence of aircraft.
Most of the thrill of skydiving is the diving part not the leasurely float with a parachute. So it tends to only be used with novices wanting to train the parachute control itself.

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What are the differences between a thin and a thick duct wall?
As can be seen on this image, these two similar aircraft, though they have different prop size they also have very different duct wall thickness.

source source
What are the differences(performance, aerodynamics, etc) between having a thin vs thick duct wall?

G-FANS, I see what you did there

It looks like the first aircraft is a testbed for the small Turbomeca Astafan which was not developed further than the two prototypes. I wonder whether the nacelle was a complete one, the definitive full inlet duct might be missing. Here is what seems a more complete one.

The thickness of the duct wall is related to the radius of the inlet lip, but is not quite the same thing. A larger radius is better for off axis flow as in takeoff/climb. The more gradual turn of larger radius keeps the flow attached where the tighter turn of a smaller radius tends to make the flow separate, creating drag and reducing efficiency of the fan.
The opposite is true for high mach subsonic flow where more air is displaced by the large radius, tending to cause shock induced separation. The small radius is easier to keep shock free and has less of a problem.
In supersonic flow the large radius design creates a detached shock wave where the small/sharp radius can keep the shock attached to the lip, which is used to enhance pressure recovery in the inlet.

So the first aircraft in the picture is supersonic

@sophit . No guarantees anyone uses them correctly.

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Has a tire ever exploded inside the Wheel Well?
Amidst the recent Delta tire explosion case with multiple staff fatalities at ATL airport, I wonder if there has been a case where a tire has exploded inside the wheel well?

Yes, of course.
One famous case which eventually led to the use of non-flammable hydraulic fluid was a Swissair Sud Aviation Caravelle which tried to clear up low-lying fog to improve visibility in order to be allowed to take off (Swissair flight 306).
For this, the pilot ran the engines at elevated power and applied brakes, taxiing up and down the foggy runway, which was Swissair standard procedure at that time (1963). The trick worked, exhaust heat made the fog disappear and the airplane could start its journey.
What the pilots did not know: The brake disks were glowing red hot at this time. With the gear down, cooling was already marginal, and once the gear was retracted, the heat quickly dissipated into the magnesium wheel hubs and the tire pressure made them explode. One of the hubs did even disintegrate during take-off, leaving magnesium debris on the runway.
With the still glowing disk brakes and shrapnel from the wheel hubs having cut the hydraulic lines, the hydraulic fluid ignited and started a fire which caused the plane to dive into the ground 35 km from the airport.

interesting technique to disperse fog, didn't knew about it.

The investigation report (German) says that a fire already started on the runway, after the first wheel flange burst (not the tire, btw - not sure whether OP cares). It did not reach a conclusion whether the second wheel burst due to overheating by itself, or due to the fire caused by the broken wheel after gear retraction.

https://admiralcloudberg.medium.com/fire-in-the-fog-the-crash-of-swissair-flight-306-c54893961151

I have an idea: What about if instead they had taxied down the runway few hundred feet, put parking brake & full throttle & back to idle, then move forward again ,few hundred feet more and repeat the process until the required runway distance needed. I don't know how many feet they needed but something like 8 stops? or am I under estimating?

@Gabe: With your proposed technique, by the time they'd reached the end of the runway and returned to the takeoff point the fog there'd've had more than enough time to descend again.

@Vikki yeah I thought about that later I think you're right. I think is time for a new type of invention. There are snow blower, now we need a fog blower. It would be a big turbine
attached to a truck/tug and it will taxi down the runway lol.

@Gabe Actually, the recommended technique was like that: Stop, let the engines blow a tunnel into the fog, move forward, repeat. However, you need to wait to let the engines spool down before releasing the brakes and to spool up after coming to a halt again. The Swissair pilots took shortcuts.


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Does obstruction in one side of a Y/bifurcated inlet can cause asymmetric thrust?
In an airplane with Y/bifurcated inlet If for whatever reason one side of the inlet is obstructed would this cause to roll/yaw or the aircraft would stay stable.

And in another setup, If instead there are 2 engines at the beginning of the Y/bifurcated inlet and there is one engine failure, would this cause asymmetric thrust?

In an airplane with Y/bifurcated inlet If for whatever reason one side of the inlet is obstructed would this cause to roll/yaw or the aircraft would stay stable?

I refer to the middle configuration in your picture.
If one side get clogged the following would be true:

The clogged side would increase the aerodynamic drag; this might indeed create a yawning moment but, due to the short lever arm, the moment would be negligible; and there would be no problem at all for the rudder to counteract it;
Half of the inlet area would miss; the working inlet might compensate for it but for sure not in those situations where a lot of thrust i.e. air is needed by the engine(s), at take off for example; surge of the engine can be expected in those cases;
Flying in a sideslip toward the clogged side of the inlet would worsen the situation due to the fuselage "shadowing" the working inlet.

In the other case where we have two engines,   one left and one right, the situation would be similar, with the clogged inlet (i.e. not working engine) also creating drag and therefore yawing moment; also in this case the rudder should be able to compensate for it and this situation might even be the dimensioning condition of the rudder.

You might be thinking that the inlets will make thrust because they're sucking air in. That's true, but jet engines push a lot more air out than they pull in. I'm not exactly sure of the ratio (it also varies for different engines), but it's more than you'd think.
As the comment on your question said, the obstruction might produce a torque, but it's close to the centerline/CM, so the vertical tail would be able to easily account for it.
In your second picture, the asymmetric thrust would probably double. (saying this because there are 2 engines, and they're not splitting a duct) It depends on the thrust of the engines and what power setting they are at, but it might start to become noticeable. If one engines is full AB, and the other is idle, you might start to feel asymmetric thrust. I'm not exactly sure how much air each jet engine would pull in, so I could be wrong.
If you want to get more complex, it also would depend on the size of the vertical stab, and the amount of rudder authority you have.

The thrust will be symmetrical -- by the time the air goes through the engine, flow will be pretty uniform.
That said, non-uniform inflow will make it easier for the compressor or fan to stall and can cause other problems for the fan.

Well, thrust-reversing (by running the motor backwards) is starting to become popular on Electric Ducted Fan radio-controlled model airplanes, which are often very realistic scale models of full-scale jet airplanes.  So in such a model of something like a F-35 or any other a/c with a Y/bifurcated inlet arrangement, there would surely be some noticeable yawing affect if one inlet was somehow blocked while the motor was running backwards!


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Engine failure after takeoff during IMC. What to do?
Flying a Cessna 172 with IFR you have engine failure after takeoff at 500ft AGL during IMC, visibility 0/0.
What's the procedure?

There is no time for a "procedure". You save yourself however you can. 500 ft is high enough for a turn around to the airport and I would simply start a 30 deg banked turn to a reverse heading (into the crosswind if there is one) plus a little extra to get you back over the runway, and land on whatever presented itself when the surface came into view.
I would do the quickie checks like carb heat, mixture, mags, mayday, etc once established in the turn. You drill that stuff to death so your hands just fly around automatically doing those things while you concentrate on flying with your other hand. Leave the flaps up until you've completed the turn and can see the surface, and side slip aggressively if you need to lose altitude.
Too low to turn around? The old saw applies; fly it all the way until it's not flying any more. Contact with ground features while under control are much more survivable than while in a spin.

I disagree that 500ft is enough for a 180 back to the airport in a C172, that's heavily dependent on weight, conditions and terrain.

@GdD 500 feet is plenty even at gross in a 172.  He said IMC and specified 500 ft.  The alternative is terrain or a building you see at the last minute.  Bloody right I'd go for the turn back from that altitude. In a normal circuit/pattern you make a turn to final at 500 ft, A 90 degree turn. You think you roll out of a turn to final initiated at 500 ft AGL too low to turn another 90 degrees?

Visual conditions are one thing, but attempting a turn at the edge of the performance envelope in zero visibility is something I'd only do if the other alternatives were worse. If there's farmers fields ahead there's no point in risking a stall-spin fatality.

YOU DO WHAT YOU BRIEFED!
This is a great example of why it is important to brief each takeoff.  Have you become familiar with the airport environment.  Where is a safe place to land if an engine fails.  Thorough preflight planning will allow you to determine the best possible outcome for the takeoff today.
It may be possible to turn 180° at 500 FT AGL, but it is quite dependent on atmospheric conditions and weight.  To land on the opposite runway you will need to turn more than 180° to align up with the opposite runway.
At my home airport, there is quite a bit of flat land at the end of the runway that will allow me to land relatively safely if an engine failure does occur.
Every takeoff is different and a proper briefing will allow you the best survival outcome in a situation like you described.


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Whats the purpose of slots in wings?
As mentioned by the person in this video, what's purpose of the slots in this Ray Stits Sky Baby airplane?

(source)

The purpose of a slot is to correct the direction of airflow over that portion of the wing at high angles of attack, to delay the onset of flow separation which leads to a stall.
Putting slots near the wingtips helps prevent a stall which starts at the wingtip first. That sort of stall is particularly dangerous because the lever arm for lift generated in the tipmost portion of the wing is equal to the whole length of the wing. Any change in lift there will produce a particularly strong roll moment which will tend to flip the whole plane over on its side and into a spin.

You'll notice here that the upper wing is mounted at a higher angle of attack.
Curiously, the wings are in a "reverse stagger", meaning the rear one will stall first.
The plane was made to be the smallest in the world, but probably after noticing this design "oopsy", the slot was added to improve safety.
Oh, if they had only made it a monoplane with folding wings.

are you sure it's not some perspective bias that seems to show greater incidence on upper wing? unable to find full scale aircraft plans, it seems rc plans show identical incidence on both wings or even higher incidence for the lower wing.

@user721108 there are pictures in reference "here".  Have a look.

have a look at pictures 2 and 7 I still think you were fooled by the vanishing point / short focal. have a look here

@user721108 that's on paper, rather than the actual plane, but I see your point.  See 2nd photo down on the right.

it seems no plans exist for the full scale machine. you can read about how quarter scale plans were made 30 years later and download those here


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Are there carbon fiber wing spar pins?
Thinking about parts and weight saving, I've never seen a pin made of carbon fiber, is there such a thing for the aviation industry?

Not that I know of, and at first glance it seems like a bad idea.
Carbon fiber is great in tensile strength (and compression, if properly supported), but spar pins are mostly loaded in shear. In composites it is the matrix, not the fibers, which transmit shear. Compared to steel, epoxy resins are really poor in shear transmission.

Even Graphlite pultruded rod which is 300ksi+ tension and just under that in compression, and probably the best material for a spar cap there is, wouldn't do well as a bolt.

@JohnK. Gotcha.

@Peter Kampf, I kind of get what you mean but can you expand a little bit, specifically  about the shear matriz and  fibers. I think this would be good for general knowledge.

@Gabe, compare it to reinforced concrete being used in some shearing load application, like a giant reinforced concrete shear pin holding up a bridge. The rebar doesn't help because the load is across the bars, and the concrete itself is only strong in direct distributed compression, with relatively little shear strength. Just replace the concrete part with epoxy resin and the rebar with  glass or graphite.

@JohnK ok now I get a better visual idea and understand better Peter's answer.

Also my understanding is that carbon fibre itself is weak in shear, which is why it cam be cut with scissors. Fancy winding patterns can only go so far to make it strong to e.g. bursting pressure in the case of air bottles, the epoxy is basically there to restrain the fibres in relation to each other rather than to provide strength itself.


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Is there any airplane that doesn't use a headset but speakers?
I wonder if there is any aircraft that is quiet enough that allows talking/listening via speakers?

I guess the obvious candidates would be lighter-than-air craft, particularly helium-filled vessels (hot-air balloons are noisy when the burners are operating!).

All our club's sailplanes have speakers. We don't even have GA plugs installed.

@rgeorge what about the mic, do you still have to use a hand/head mic?

there's a tiny mic on a gooseneck attached to the plane.

@rgeorge I'm confused about what is the gooseneck exactly. and What aircraft are you talking about exactly? or do you you have a picture link?

This is in a Blanik L23. Not unlike this one: https://www.cumulus-soaring.com/store/dittel-dynamic-gooseneck-microphone , or maybe a little longer. It's screwed to the right longeron next to the pilot's head and wired right into the radio

@rgeorge Interesting setup, thanks for the link. I have a clear picture now.

The short answer is yes: gliders (sail planes.)
It is common in gliders to mount a hand-held radio onto the instrument panel or use a built-in radio with a speaker and boom mic.
In most powered aircraft, however, pilots generally prefer headsets, except perhaps in vintage or ultra-light aircraft that don't carry a radio. Here's why:
Using headsets in an aircraft cockpit achieves five main things:

Reduce background noise from engine and airflow, making time in the cockpit more comfortable and reducing the risk of long-term hearing damage.
Allow the crew to converse via an intercom system.
Make it easier to listen to incoming radio signals by cutting out distracting noise.
Make outgoing radio signals clearer by allowing the microphone to be situated close to the pilot's mouth at all times.
Allowing both hands to be used for flying, instead of needing one hand to hold a microphone.

The cockpit of a modern jet aircraft is certainly quiet enough that speakers could be used, and sometimes are, but items 3 to 5 above still apply. Headsets cut out background chatter and make it less likely that crew will miss transmissions from ATC.
The older Cessna designs used to have a loud speaker on the cockpit ceiling and a hand-held microphone. They weren't any quieter in the cockpit than they are today, though. I guess people didn't worry so much about hearing-loss back then!

I learned to fly in C150 many years ago and the instructor clued me in to crank up the speaker volume and use foam ear plugs. So nice now to have sound cancelling or just sound deadening headphones and not have to fumble around reaching for the mike.

@AeroAndy I wore foam earplugs for years but they are fairly useless in airplanes protection wise because the bulk of the noise is in the 70-120Hz range, where there is very little attenuation. However foam earplugs are a good supplement to ANR headsets that don't attenuate higher frequencies very well, if you really want to protect your hearing. Absent an ANR headset, I now use 3M plug-ins with several grams of lead tape wrapped around the shaft and covered with heat shrink. The low freq attenuation is nearly identical to my Zulu 3.Turn the ANR off while wearing them, I can't tell the diff.

@AeroAndy, I remember those! https://aircraftpartsandsalvage.com/wp-content/uploads/2018/04/products-62800-000_248.jpg

Is there an airplane that doesn't use hand/head mic?

@gabe as mentioned in my answer there where production aeroplanes that didn't use headsets. Older biplanes didn't have them at all. In the early days of flying in England, they used a speaking tube called a "Gosport Tube" to communicate between student and instructor. These days, however, headsets can be retrofitted in almost any aeroplane so the choice ultimately down to the pilot (crew) and whether or not radio is being used. There isn't a specific type of aircraft in which there is no option to upgrade to a headset, so pilots will generally choose to do so, or just go non-radio.

5 is the opposite on a jet. With autopilot being basically mandatory in cruise, you need a means to conveniently activate the PTT that keeps the pilots hands away from flight controls and ideally other controls. So you end up with a handheld PTT switch, and there's little difference to go from that to a hand mic.

Yes, the Boeing 737 is too loud for this but the Airbus A320 and Boeing 777 are two aircraft that I know with this system.
A320 has a speaker located inside the cockpit. Below is an image of the A320 controls for the loudspeaker.

Pilots can either use this or their headsets.

I think the things circled in the above image are the speakers in the A320 but I'm not sure.
There was one notable incident of Northwest Airlines Flight 188 where the pilots removed their headsets, took out their laptops and were using these speakers. They didn't listen to ATC and overflew their destination by about 200nm

He explains a bit about the speakers in this video.

does that speaker also has a microphone or they still have to use a head mic?

@Gabe, as shown in the video at 8:38, there is a hand mic available in the A320 that they can hold like a singing mic and speak

Loudspeaker location.

I guess there are no aircraft without hand/head mic then?

Nowadays the headsets are the "gold standard" in aviation, but in the olden days most aircraft, at least general aviation ones, actually came standard with the handheld microphone / speaker configuration.
Headsets have become so lightweight and comfortable that there really is no reason not to use them.

The big issue was cost, more than comfort. A headset is a big step up from the speaker and hand mic. DC, Telex , and couple others had a near lock on the market with their patents. When I started flying in 1988, the cheapest DC headset was over $600, equivalent to about 15 hours of solo. That year many of their patents expired and by the spring of 1989, there were a half dozen competitors selling headsets for about $250.  That's when I got my first one.


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Can tail wing increase and main wing decrease(so they're equal size) achieve same total lift?
Thinking that though is not happening every day, collisions with other planes wing during pushback/taxi occur here and there, and also that the wing size limits the parking/gate space specially for big airliners and small/crowded airports, I thought if designing an airplane in a way so that you could reduce the main wing span and increase the tail wing span so they are equal and as a result the aircraft's maximum span is reduced, then would this help to alleviate the problems described(collision and parking size)?
Would this work, or the pros would be less than the cons?

That design is called "canard" and there's literally hundreds of answers about its pros and cons and many other aspects.

Thanks for reminding that, I totally forgot, but it seems the https://en.wikipedia.org/wiki/Wing_configuration#Tailplanes_and_foreplanes design  I was describing is more like a https://en.wikipedia.org/wiki/File:Wing_tandem.svg Tandem instead of https://en.wikipedia.org/wiki/File:Wing_canard.svg Canard

Yep, tandem is the more correct wording

You have a fundamental misunderstanding about the tail of a conventional aircraft. It produces download, not lift, and is used to allow aircraft cg to be ahead of the wing center of pressure, making the aircraft stable. Tandem wing and canard aircraft are different designs.

Even on aircraft carriers, where hangar volume and apron area are much smaller than on land, tandems are vanishingly rare.

Yes, same total lift can easily be achieved by 2 pairs of wings - or 3 pairs, or more, as in the Caproni Ca.60 above. But there is a reason why monoplanes are in fashion, as mentioned in this answer: drag.
The two well known basic subsonic equations:
$ L = C_L \cdot \frac {1}{2} \rho \cdot V^2 \cdot S \tag{Lift} $
$ D = C_D \cdot \frac {1}{2} \rho \cdot V^2 \cdot S \tag{Drag}$
With S being the wing area, in whichever shape. But for the drag coefficient $C_D = C_{D0} + \frac {C_L^2}{\pi A e}$, the wing aspect ratio $A$ plays a large role in induced drag, as per this answer.
Dividing a wing area into two or more pairs of wings reduces their aspect ratios, and creates more induced drag than just one single pair of main wings, with as high an aspect ratio as structurally possible.

An overarching consideration for a commercial airliner designed to be used at gates is that aerodynamics, while important, can’t be, well… overarching all other requirements.
General Challenges of Dividing One Wing into Two:

Duplicity of systems (cost, weight, complexity)
o   Flaps
o   Ice Protection
Thinner wings (assumes t/c_max ~same, resulting in smaller t_max's)
o   Gear integration disadvantages
o   Less thickness for flight control actuators

Challenges Unique to One Wing Aft of the Other:

Gear integration (e.g., neither wing will likely be near a good rotation point)
Ground footprint has less maximum width but consumes more area
o   Maneuvering GSE around aircraft perimeter
Stability & Control
o   Requires statically unstable aircraft in pitch for both wings to be lifting
o   Regulatory hurdles
o   Technical and safety risks
Propulsion Integration
o   Will want the weight of the engines between the wings
Wake/downwash effects of forward on aft wing

Challenges Unique to One Wing Over the Other:

Highly coupled lifting surfaces in transonic flight
Structural issues with flexible high aspect ratio wings, one over the other

In summary, it’s theoretically possible but there exist serious (insurmountable?) challenges in creating a workable system solution.

There is a loss of efficiency as now one essentially has a bi-plane.  However, one should not ignore this design as it may allow for higher aspect wings.
Design proposals for "trussed-braced" wings could be further developed.
Bi-planes undeniably can generate more lift at the same speed than monoplanes, which may be useful in applications such as military cargo transport.
Very large bi-planes have not been tried in over 100 years.  The ones that were built were said to fly well.

Also, consider that one wide span wing gets to deflect a wide swath of air while two tandom wings of half the span both deflect the same swath of air. The latter is effectively half the aspect ratio which results in higher induced drag and resulting fuel use.


text:
Why aircraft don't have integrated scale?
There have been some accidents due to wrong weight calculations that ended in fatalities, both in comercial and private aviation.
Besides this, though it is a simple task on the pilot's flight check list, it is a task. So I wonder, why don't aircraft have a built-in scale that would solve this problem and accurately give the total weight of the aircraft so it is safer and also one less item the pilot has to do.

(Aircraft scale source)
Instead of using a balance like the image above, it could be something installed inside the landing gear shock strut/cylinder that depending on the bar level it could tell the weight of the aircraft.

(source)

Does this answer your question?  https://aviation.stackexchange.com/questions/1850/do-some-airplanes-have-weighing-scales-on-the-landing-gear

I thought the same but could not find anything...

@MichaelHall i think it does. I didn't buy the point one made saying "because airplanes have wings" .... c'mon, a A320, B747, A380 ? c'mon....I wouldn't buy that even on a ultralight, not even on a glider lol....you would need a lot of wind around those wings ....

Because you don't actually care about the weight on the landing gear, you care about the mass of the aircraft. A scale in the landing gear would measure the weight, which is force that is currently applied to the scale. However, this is not only composed of the aircraft mass, but it is influenced by many factors (wind, temperature/humidity, inclination of the ground, unbalanced load, ...) that would lead to an inaccurate readings.
When aircraft are weighted during their periodic checks, this operation is done in a controlled enviroment, usually an hangar, which special scales. For example, this scale:

It uses external sensors to determine the inclination of the ground and provide an accurate measurement. Still, it works reliabily only for 1° maximum of inclination (ref. product page).
In conclusions, you can put a scale in the landing gear, but a light wind pushing on the bottom of the wings would result in a smaller value, which is dangerous. Moreover, you still need to calculate the weight distribution. So, it's simpler and safer to compute the mass, rather then derive it from the measured weight on the landing gear.

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Why do we have a booking code and a ticket number?
As per subject why is this done? Doesn't it make operations more confuseing as we have to references for every single passenger? A ticket number seems to be unique so why is this not used for all passenger references?

You might get a better answer on travel.SE; ticketing questions aren't usually related to aviation as such

Part of it is a hold-over to historical systems (where airlines ran their own booking systems). Now that most airlines use a global system like Amadeus this is less of an issue.
The ticket number (PNR) and booking number (record locator) do have slightly different purposes though. The former contains the details needed for the actual flight (your name, contacts details, flight numbers, etc) while the record locator can also contain other information not directly related to the flight.
In short: The record locator contains a reference to the PNR but can also contain additional information that is not contained in the PNR.

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Do airlines schedule departures based on average environmental conditions of departing airport?
I have noticed that at Dar es Salaam International (HTDA, Tanzania, Africa) all major airlines (namely KLM, Swiss, Emirates, Turkish) schedule their departures mostly at night starting from 10:00 PM local time onwards.
Besides the fact that they have to match their flights with ongoing connections, I was wondering if they do this because they fly here with big aircraft (A330-300, B777, B737-900ER) and the airport, even though being at sea level, has very high day temperatures throughout the year (30C and higher).
Maybe this helps during takeoff, which in hot conditions could be risky, especially if fully laden?

Interesting. Just checked now and current temp is 8 degrees celsius. Here in TZ it is constantly 30

Curious that KWI has 10015 feet runway and DAR 8582 feet.

What about Kuwait City with seems to be hot too?

https://weather-and-climate.com/average-monthly-Rainfall-Temperature-Sunshine,Dar-Es-Salaam,Tanzania

My guess would be this has more to do with logistical reasons than technical limitations.
It likely has something to do with airline schedules in European / North American airports where there can often be a night-time curfew in place at airports due to noise concerns etc.
e.g. I remember Frankfurt till recently at least didn't allow scheduled international landings before 05:00.

Ergo, you need to make sure you take off from  Dar es Salaam etc. at times that will ensure a landing slot at EU that won't infringe on the curfew. Many flights even to non-EU, western destinations from Dar es Salaam likely connect via EU hubs.
More details at this link about curfew times at various EU airports:
http://www.zurich-airport.com/the-company/media/current-topics/night-flight-ban
A part of this can also be the greater (i.e. worse) elasticity of booking response to odd / inconvenient flight times in wealthier markets. i.e. One uses up the best slots for  wealthier intra-EU markets for the most elastic customers & then whatever slots remain go to longer, international routes irrespective of the late night slot that results at the destination non-EU airport. i.e. An airline route scheduling team cares far more to ensure departure / landing times on a Copenhagen-Stuttgart flight remain convenient time slots than to try and keep a  Dar es Salaam departure daytime.
Also, in the intra-EU markets there's competing modes of travel. e.g. Confronted with an inconvenient 23:00 flight a business traveler might choose a 17:00 train instead.
On a Dar es Salaam to Europe sector there's really not any non-air-flight competition for passengers. So one can afford to keep inconvenient local time departures and still expect no penalty from passengers voting with their feet. Of course, this can only be stretched so far because at some point a competing airline can launch a more conveniently scheduled departure. Or as a second order effect tourist traffic can switch plans to alternative destinations etc.
Incidentally, on a lot of Indian subcontinent sectors as well departures to EU were traditionally crowded in the 23:00 to 05:00 time slots.

Prague airport is closed after midnight as well. This resulted in too many flights scheduled at 23:55 which regularly get delayed and depart after midnight.

In general, high temperatures affect the performance of the aircraft in two major ways:

As the density is lower at higher temperature, the thrust produced by the engine is reduced.
The lift produced is reduced as lift is proportional to the density.

Due to these reasons, an aircraft operating in hot condition will have to either reduce weight for taking of from a fixed runway length or increase the takeoff run for taking off with the same weight. Also the climb performance will be affected at high temperatures.
Due to this, the airlines could've schedule operations in conditions when the temperature is less if they believe that takeoff weight is critical for example, in long range fights or where a set number of passengers is necessary for economical operation.
However, this problem is mostly critical in case of 'hot and high' airports. In this case, this is most probably for facilitating the arrival of passengers in destinations in the morning.
For example, the SWISS 296 leaves Dar Es Salaam at 11:20 PM (its connecting flight lands only at 1005 PM) and reaches Zurich at 06:16 CET.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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Why are 4 engine civilian turboprops not produced anymore
As per subject why are 4 engine turboprops not produced anymore for civilian flights if turboprops are so efficient?
How comes the military still use them (see Airbus A400 and C130)
It would be amazing to fly on a 150 seater powered by 4 propellers.
What favours jet engines?

Well, military turbo-props are supposed to carry a large load at lower speeds, they wouldn't work well in passenger airplanes now because a jet plane can carry the same amount of passengers for a longer distance and faster than a turbo-prop can. However, they still use double-engined ones because they fly short, low-density routes to save money over using larger jet planes.


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What is a take off roll?
Reading about 737-900ER take off roll (3000 meters) from another question, I would like to know what this means.
Is it intended that the aircraft needs 3000 meters before it can pitch up to take off or at 3000 meters is has acquired sufficient height and should be airborne?

I think part of the confusion about this term arises because, in aviation, the word roll is used for two rather different things.

@OwenBoyle Saw this question on the hot network list and came here to see if an aircraft could really take off and immediately do a roll...

@Michael: some aircraft actually do it.

@BogdanWilli Not sure if serious...  That's a great video, but was taken from a game.  Not real.

@JPhi1618: You got me! But this one is not from a game.

The take-off roll, also called ground roll, is the roll distance before the aircraft becomes airborne.
In case of the 737-900ER, it will be in the order of 2000 meter.
The quoted 3000 meter is probably the take-off distance required (TODR) or take-off run required (TORR) at maximum take off weight. That assumes a full throttle acceleration to about half of the runway (1500 m), then an engine failure, continued acceleration on a single engine, rotation and take-off at 3000m. In case of TODR, the climb to a height of 35 ft is included as well (for FAR Part 23 aircraft it is 50 ft).
This means the 737-900ER requires a runway of 3000 meter length to take-off with an engine failure or to stop when the failure happens before the decision speed (V1). Since engine failures are unpredictable this is the minimum runway length required for take-off planning.
This all assumes ICAO standard atmosphere conditions. For runways at higher altitude ( > MSL) / higher temperature (> 15 deg C) the TORR will be even higher.

As far as I can remember take off distance includes a height of 50ft, can you cite the 35ft?

@falstro Originally I typed 50ft, then changed it to 35ft, because I thought the 50ft was for props, 35 for jets. I will verify the numbers

@falstro 50 feet is indeed for piston transport, 35ft for jets (the 707 & dc-8 could not make 50ft at some of the available runways at the time). It is 15 feet on a contaminated (wet) runway.

interesting, thanks!

@DeltaLima: 50ft is FAR/JAR part 23, 35ft is part 25 (25.113(a) to be precise). An ATR-72's takeoff ends also at 35 ft.

@PeterKämpf Thanks for clarifying, I didn't yet have the time to look it up in the regulations. Will update the answer at later moment.

I was going to say, 3000 meters take-off roll had to be an error.

Take Off Roll is defined as:

The process whereby an aircraft is aligned with the runway centerline and the aircraft is moving forward with the intent to take off. For helicopters, this pertains to the act of becoming airborne after departing a takeoff area.

H/T @mins for the link.

737's typically take off in 3000 to 4000 feet depending on cargo and configuration.
The TORR and other statistics are runway length guidance figures that are much longer than the actual distance the aircraft rolls before it leaves the ground.

The question arose due to another question regarding the 737-900ER, which requires a lot more runway than most 737s for takeoff (2,000 ft. more than a -800 and 4,600 ft. more than a -700, according to the 737 NG Wiki.) That's assuming MTOW/standard atmosphere for each of the above.


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What happens when the eigenvalues of the longitudinal A matrix in dynamic stability analysis, are NOT two sets of complex conjugate pairs?
The complex conjugate pairs of eigenvalues of the longitudinal A matrix characterize phugoid and short period dynamic responses, this information is well established.
My question is - what happens when the eigenvalues consist of 2 real roots and 1 complex conjugate pair?  Can this happen (assuming no error on input, or does it only happen with an error?) and if it does what does this say about the dynamics of the system?  Examining the eigenvectors I'm wondering how to interpret two eigenvectors that consist of all real values?

Thanks!

Does this have anything to do with aviation? I have no idea. Looks like it might be better suited to Math.SE, perhaps.

@RalphJ, it definitely has something to do with aviation, specifically aircraft design. Definitely not appropriate for math.se, because it concerns physical interpretation. physics.se, might work, but it's not off topic here either.

@JanHudec Fair enough. Close vote retracted.

So, I saw this in the Close queue, which didn't show any answers and thought, most people will go to XKCD for an obligatory answer. I remember I thought, how long before we get a Peter Kampf obligatory answer. Got through the queue, came here and .... :)

what happens when the eigenvalues consist of 2 real roots and 1 complex conjugate pair?

This means that the one complex conjugate root is still an oscillation but the other has split into two aperiodic movements. One of them should be a positive and the other a negative real value. While the negative root signifies a damped, aperiodic movement, the positive root shows that the airplane has one instable, divergent mode.

Can this happen?

Yes, for example when the center of gravity is moved aft of the neutral point, the phygoid will split into two real roots. The positive one describes the divergent behavior when static stability has been lost.
Backgound:
The equations of motion describe how acceleration, speed and pitch rate of the airplane react to small changes of the control parameters (elevator angle and throttle setting). They are second order differential equations and can be solved similar to systems of quadratic equations where the coefficients form the elements of a square matrix. The eigenvalues of the matrix describe frequency and damping of the movement which is caused by changes to the control parameters while the eigenvectors describe how acceleration, speed and pitch rate are affected in detail.
Note that this only concerns longitudinal movement (forward-back, up-down and pitch). The equations can be expanded to cover roll, yaw and left-right movement as well, but the question only concerns the simpler longitudinal part.

That would make sense in the case I'm evaluating Cm_alpha is positive.  Do you have any references for this, a text, paper, link etc I'd like to learn more about this!  Is that the only scenario in which this occurs?  Thanks :)

+1, but probably really shouldn't be ... after all, the upvote description is "this answer is useful" ... seeing that I can read English words all in sentences, it's an answer; it's probably a valid answer.... but to me? Not very useful.... well done Peter, as always.

@CGCampbell can you be little more clear on what you mean?  Are you complaining about the quality of the answer or the question?

@spacegirl1923: Try this. Or this

@spacegirl1923. The last 5 words are the key to CGCampbell's comment -- most folks who fly airplanes have no idea what eigenvalues are & what they're used for.  Peter, being both a pilot and an engineer, is an exception to that generalization.  Added to which, he's wicked-smart on this stuff & exceptionally willing to help out with questions that most of us don't begin to comprehend.  Nothing wrong with the question -- if Peter believes that it's worth the time to answer, then your question was fine.  And I'd trust an answer you get from Peter any day of the week, and twice on Sundays!

@spacegirl1923 Exactly what RalphJ said. Peter Kampf is that rare breed of a wicked smart and talented (obviously) engineer, who is also an avid pilot (and if I recall correctly, glider pilot) who has the ability to answer technical questions succinctly and in language understandable to his audience. You asked a question I could never understand and Peter answered it to your satisfaction. Not the first time he has done that, nor will it be the last, I am sure. It was my ham-handed way of complimenting him.

@CGCampbell I hope my last edit made the answer more useful. Well argued criticism is always welcome. I have learned a lot here from researching answers to questions I would never have asked myself.

@PeterKämpf you're first unedited answer was sufficient, the last paragraph above I assume is for other readers of this question :) the Princeton ref where it breaks down the effects of the dimensional derivatives on roots of the characteristic equation is really what I was hoping for! Twas feeling a bit lazy and didn't want to work out all the math for myself - thank you.  It's an unconventional design, with several unique parameters, but I hadn't made the connection that + cma would move a set of eigenvalues out of the complex plane.  Good to know!

@RalphJ & CGCampbell  - thanks lol :D being an infrequent visitor to this forum I hadn't picked up on that.

@PeterKämpf are there cases where roots are real and both are negative. Such as, suppressing phugoid with flight control computer and it becomes non-oscillatory?

@Kolom: Of course, with computer control everything is possible. Until the unstable frequency exceeds the rates of the servos needed to move the control surfaces quickly enough, that is. But I wonder how a complex software can be modelled by a second order inhomogeneous differential equation so it can be shoehorned into the system of equations ;-) Sometimes it is just enough to increase the damping term (first derivative) and have a negative second order derivative (negative feedback) but that doesn't do the limits of software any justice but assumes it works perfectly in all cases.


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Pilot age limit to serve as required crew on an FAR 135 flight into Mexico?
Curious to know if Mexico has filed a difference to the ICAO Annex 1 limitation of age 65, which would permit pilots over age 65 to operate a commercial flight into Mexico.


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how can we calculate normal force or vertical component of propeller in an aircraft?
when we calculate thrust of an propeller engine we also face to vertical component or normal force which change neutral point of an aircraft how can we calculate this force? thank you

There is an old NACA report (NACA TN 2586) on this by John L. Crigler and Jean Gilman, called Propellers in Pitch and Yaw


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What commercial airplane broke the sound barrier in 1979?
I’ve racked my brain and Google for a few years and can’t find an answer. I’m hoping someone here can help. In 1979 I flew from Chicago to Cologne, Germany. I distinctly remember the pilot informing us in an announcement that in a minute we would hear a loud boom and to not be alarmed. It was the sound of us breaking the sound barrier. It was my first ever flight when I was 17. I thought I kept the ticket, but can’t locate it. Any idea what the plane would have been? Concorde? Or were there other planes that did this is ‘79 over the ocean?

Was this a scheduled flight?

Umm...  You don't hear a boom if you are inside the airplane.

I wonder... Do passengers in other planes nearby hear the sonic boom of a supersonic aircraft passing nearby?

In a strong enough tail wind conventional airliners have had a groundspeed faster than the speed of sound, but of course it's the airspeed that matters:  https://www.washingtonpost.com/weather/2019/02/19/flight-reaches-mph-furious-jet-stream-packs-record-breaking-speeds/

That's not how sonic booms work. The sonic boom is continuous. That is, it is not a single boom but a constant loud RAWRWRRRWWRRR from the moment the plane breaks the sound barrier to the time it slows down below the speed of sound. The reason people on the ground hear a single "BOOM" is because the're standing at a single place. If you place an array of microphones along the flight path and combine all their outputs it would not be a single boom but a non-stop RAWRRWWRRWRRR. Of course, you cannot hear this if you are on the plane generating the "BOOM"

... having explained how sonic booms work my guess is either it is a false memory (don't worry, this is very common, check out the "Mandela effect") or it was a dream.

If you had been on a Concorde flight, you would remember it as distinctively different to other airliners. The cabin is quite narrow (2+2 wide) and low. The nickname of "World's largest jet fighter" has some truth to it.

The more likely cause of that boom would be another plane nearby flying past at more than Mach 1.

Although Concorde flew to many cities on charter flights, including to Cologne and Chicago, it is pretty unlikely that you flew on Concorde between those two cities. Not that it was impossible, as in theory there could have been charter flights between Chicago and Cologne with refueling stops in New York and either London or Paris. And of course the over land segments would not be supersonic. Not really practical from a time savings standpoint, but that wasn't the point, people just wanted to ride on Concorde.
However as explained in this answer, no you would not have heard a sonic boom if you were on Concorde. And since all Concorde pilots knew this they would not have made such an announcement.
What I suspect happened is that you were on a regular flight across the Atlantic, and your pilot became aware that Concorde would be passing relatively nearby (likely at a much higher altitude), and they thought that there might be a sonic boom heard and that it might alarm the passengers, so they made an announcement about it. In that case you either misheard or misremembered exactly what the pilot said.
See Did Concorde's sonic booms affect other air traffic?

This makes even more sense based on the other answer saying ATC would warn nearby traffic about it.

There's be a separation of at least about 10km between Concorde and any other airliner on the route because of the different cruise altitudes, not even taking into consideration the different airways.

@jwenting - so does that make it unlikely, extremely rare, or just not something that happened every day? Concorde cruised between 55 and 60,000 feet, airliners typically between 35 and 40,000 feet. That's a vertical distance ranging between 4.5 and 7.6 km.  During climbout Concorde went supersonic at around 40,000 feet, not sure how low it remained supersonic during descent. Concorde's sonic boom was clearly heard on the ground when it was cruising at 18 km, otherwise it wouldn't have had land overflight restrictions. Of course the boom diminishes as you get further away from the flight path.

@StevePemberton at the time airliners rarely flew higher than 35000ft. Most flew around 30000. You simply wouldn't see or hear Concorde. The overland restrictions were because a) it'd fly a lot lower there (takes time to climb) and b) politics (mostly b)

@jwenting - I think the U.S. restrictions were mostly based on public sentiment in an environment where everyone from Juan Trippe on down thought that supersonic airliners would soon replace many if not most subsonic airliners, just as jets by that time had pretty much replaced piston props. The thought of enduring multiple sonic booms per day was not appealing. Of course in reality the Concorde flight rate was minimal. Was Concorde allowed to fly supersonic over Europe or was it prohibited there also? I am only aware of the Malaysia and India restrictions, which some suspect was political.

hence politics @StevePemberton . Vote (and campaign donation) buying.

@jwenting - if you are referring to the U.S., is there evidence of this in the case of the government banning supersonic overflight?

@StevePemberton one can assume everything congress does to be at least in part inspired by it. People have ideas (false or otherwise) and politicians act on that "to be seen doing something".

It is extremely likely that you misremembered this, or alternatively that the pilot was making a joke.
Reasons for this:

There has only ever been one supersonic airliner in the western world, and that is Concorde.
Concorde was only operated by British Airways and Air France. Neither of them flew scheduled flights from or to either Chicago or Cologne. It's technically possible that you misremembered a flight that flew something like Chicago->New York->London->Cologne with Concorde as the middle leg, but I assume you would have remembered that detail.
While Concorde did fly charter flights, such a flight would have been extremely memorable, far above the level of "I'm going to Cologne and it happens to be on a Concorde".
When you are inside a supersonic aircraft you do not actually hear the sonic boom.

Actually Concorde flew to a lot of different cities on charter flights, hundreds actually, including both Cologne and Chicago. In fact roughly half of all Concorde flights were charters, especially holidaymaker flights during the tourist season. Of course they would not be supersonic during the land portion of the flights. And to your point there would not have been a nonstop flight between Chicago and Cologne. But there could have been a direct charter flight between those two cities, refueling in New York and either London or Paris.

If you think that's possible then it would make a good answer.

I think your answer is correct because sonic booms are not heard in the plane creating them.

The most likely explanation is that the pilot knew that he had taken off one or two planes sooner than either Concorde, Tu144, or (much less likely that he would know) a military jet, and therefore knew that it was about to be overtaken.
As others have already said, you wouldn't hear a boom inside the aircraft that caused it, but the boom is essentially three-dimensional, so propagates all round, (not just towards the ground) so would be audible to any aircraft nearby.
There are so many reasons why you would have known that it was Concorde that you were on, that it is totally unreasonable to think that it was indeed Concorde that you were flying on.


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Need help with a military aircraft ID
I found this photo going through some of my mom's pictures.  I would like to know what type of aircraft this is.  I believe they flew from he UK, possibly to Scott AFB or perhaps Griffis AFB.  Time period I estimate at 1958.  Any help appreciated!
Thank you

C-121. Military version of the Lockheed Constellation.
https://en.wikipedia.org/wiki/Lockheed_C-121_Constellation


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What is the name of the dotted line that shows the predicted turn radius, found on the Navigation display of the 738
What is the name for the white dotted line that stretches out from the aircraft on the navigation display, when the aircraft enters a turn? It shows the aircrafts predicted flight path.

Do you have an image?

The segmented white line is called the “Position Trend Vector”.


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How to fly a departure after a practice approach with Garmin GTN750?
I fly a C172 which is equipped with a Garmin GTN750. Whenever I shoot a practice approach followed by a published departure I run in sequencing problems. So I load and activate the approach and load the departure. As soon as I hit the runway the system asks for the missed approach which I don't wanna fly. But neither the system starts sequencing towards the loaded departure nor am I able to activate a leg of the departure manually ("activate leg" is greyed out in the flight plan submenu). I have to delete the entire flight plan and reload the departure to make it work? But why? How to do better? Is there any recommended best practice?
Thanks.

Here is what I found out:
I asked Garmin Support but their answer was disappointing. They said "it's normally the case that the departure is loaded on the ground as a way to leave your departure airport rather than an alternative to flying a missed approach, so this seems to be an irregular operation which may result in weird quirks for the system." Irregular operation? That has happened multiple times to me and it's always the case if your climb out after a practice approach is a published procedure instead of a radar vectors.
Garmin's solution is "Deleting the flight plan is an effective solution to resolving problems where the GTN wants to fly the missed approach."
Referring to the greyed out waypoints on the departure they said: "Departure procedures may involve a grey waypoint because there is an emphasis on hand flying the aircraft when departing an airport. I would recommend flying to the first waypoint manually, and then activating the route to the next available waypoint." That doesn't make sense at all and it's not a good recommendation either.
Here is what chatGPT came up with. Its answer was surprisingly good and helpful. I have verified its answer and it works:

Prepare a follow on flight plan and save it. As soon as you are overhead the runway (or later) load the stored flightplan. Sequencing works as expected.

Alternatively without preparing a new flight plan: Just switch to the flight plan menu where your departure is already loaded. Select the next applicable waypoint on the departure, hit "direct to" and "activate". Obviously for the first "direct to" portion your are technically not flying the departure procedure but should be close enough for most cases. After reaching the waypoint sequencing works as expected.


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What is the landing requirement for Klein Vision AirCar?
The Klein Vision AirCar is said to require a runway of only 1,000 ft and a speed of only 75 mph for take off.
But I cannot find any information on its landing requirement such as:

Minimum runway length for landing under optimal condition
Wingspan clearance
Optimal angle of attack for landing
Minimum speed to prevent stalling
Typical speed when the wheels touch the ground and whether there is additional distance needed (with wings present) to reduce the speed to 75 mph.
Etc.

See April 2024 news article about its readiness to sold commercially.

Soberer evaluations and reports are in https://en.wikipedia.org/wiki/Klein_Vision_AirCar#References.


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How will future NOTAM exchange world wide work with DigitalNOTAM?
As by my knowledge the world wide exchange of NOTAMs is based on the ICAO format within the AFTN - between all the ANSP, including as biggest the FAA(USA) and Eurocontrol(Europe).   This is as well by their own safety regulations.
Even the FAA provides the international important NOTAM in the standard ICAO format.
How should this work once the DigitalNOTAM (Based on the AIXM 5.1 Event Extension) is fully introduced?

The DigitalNOTAM is not 100% standardized and even Eurocontrol & the FAA do use different versions/dialects of the AIXM 5.1 and the Event Extensions.
How can compatibility be guaranteed between all the parties in the world wide Aeronautical community?

As by my understanding the AFTN network will not work with the XML based format (as the addresses are provided there not like used for the AFTN messages) - or would everybody just adapt their network clients (switches/router/message handling applications)?
I do not see there any action in that direction.

Is the idea that the ANSPs provide their data only via the SWIM interfaces?
I also see, that the SWIM "standard" is not used in the same way by all parties in the the Aeronautical community - like for AIXM.

For the FAA - Maybe not 100% related?
4.1: Is the FAA providing as well the Domestic/FDC NOTAM via AFTN or convert them to ICAO format for AFTN?
4.2: Would/or does the FAA provide the Domestic/FDC NOTAM as converted digitalNOTAM?

I do understand that both regulators EASA/FAA do say that for safety reasons the ANSPs do have to use the new DigitalNOTAM format (AIXM 5.1 Event Extension) - but do they provide more details - considering that without more details and the incompatibility between the different dialects, this will limit the safety improvements wanted.

It is difficult to speak about future. Note: having different dialects it is often not a problem (as long they are well defined): if you operate in different regulation areas you just assure your (airline) software is compatible with such areas. -- And I think you ask too many questions (which it is not good for this site format and so this site rules). Ask a generic (not too generic question), and then follow up questions. It may take more time to get all answered (I do not think), but nobody of us should invest so much time to write a book (comprehensive answer), so people may not answer

What does prevent digital Notams generated using AIXM schedules to be sent using the path of manual Notams, with or without an automated interface?


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Holding when no hold in-lieu of procedure turn present question

If I plan to do the ILS RWY 27 at Bainbridge, can I opt to hold at LYZ instead of doing the prescribed procedure turn? If so when can I descend from our en route altitude to 1900FT MSL to begin the approach?
My understanding is I can request holding and when holding complete start my descent on the inbound course. My only worry is if we have to lose a lot of altitude it could make for a difficult approach. What is the best course of action?

Note that the depicted hold at LYZ is for the missed approach procedure, not the "going toward the runway" approach procedure. I'm not actually sure if you'd be able to use it for course reversal or if you're required to fly the PT.

Is it me, or is it a bit strange that OLEEE is defined as 184° bearing to the station when it is nearly on top of the station?

@Timbo, nope, it's not just you.  Do NDBs have a much smaller cone of confusion such that you could ID the point if you were on centerline of the localizer?

@MichaelHall I would believe station passage would work (like at a compass locator) but this is defined by a bearing… bizarre!

Can I opt to hold at LYZ instead of doing the prescribed procedure turn?

You may request to hold in any manner you desire, and fly the hold however you are cleared to fly it.  Just be aware that for a non-standard request you may be questioned as to the reason, i.e. whether for troubleshooting a malfunction, etc.

If so when can I descend from our en route altitude to 1900FT MSL to begin the approach?

When you tell ATC you are ready to commence the approach and they clear you to descend.

What is the best course of action?

Fly the procedure turn as published, or request vectors to a straight-in ILS.  Why make more workload for yourself by inventing some new and unpublished procedure, especially one that puts you precariously high?


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What is the difference between SoCal Approach, SoCal Departure and SoCal TRACON?
I've heard these 3 terms in ATC recordings and on web pages. Do they all use the same frequencies and the same controllers?

Related

SoCal TRACON (Terminal Radar Approach CONtrol) is the name of the facility.
SoCal Approach and SoCal Departure are the call signs used over the radio by that facility, depending on whether the particular aircraft they’re talking to is arriving or departing. They’re the same controllers on the same frequencies.

So basically the purpose for using the call signs is to improve the situational awareness of all the parties on the frequency.

Does the same controller work approach and departure at the same time?

Approach and Departure aren't necessarily "the same controllers on the same frequencies". It's fairly normal to have them split, or at least have the option to do so

@expeditedescent The same controller will use both names as needed on the same freq. A given sector may be dominated by one or the other, but you’d never have two controllers with different freqs in the same sector.


text:
Is a non-US airline responsible for failing to cancel a flight over airspace the FAA determined was unsafe?
If the FAA determines that an airspace is unsafe, and a non-US airline thinks it knows better and fails to cancel flights
departing into that airspace, and passenger lives are lost as a result, is the airline responsible for knowingly putting their passengers in danger?
What about the PIC? Is he responsible?

Is there anything else they can even be sued for other than what families typically sue for in the event of a crash? Other than that, I’m not sure the FAA restricted flights from entering Iran or exiting Iran? I just think they had a suggestion posted?

It was a total ban on all US airlines

I think this is too broad to answer easily: the answer could be different depending on the country of the airline. It might also be 'too legal' to answer here. If you don't get a good response here, you might try law.SE.

The FAA doesn't have any jurisdiction for non-US airlines or airspace, why would they be responsible if they didn't follow those advisories? This may be better asked on Law.SE.

I'm voting to close this question as off-topic because this is about law and liability and would be better on Law.SE.

@RonBeyer, because they knew it was unsafe

Unsafe by who's standards? Would it be unsafe for a US airline to fly over Iran right now? Yes. A Russian one? Nope. Lebanese? Also no.

@RonBeyer, that forum might get better answers in "legalese" language, but as long as there is a legal tag in the aviation forum this sort of question is on topic.

@MichaelHall The tag description is "Refers to any question related to the application of laws in aviation." This is not the application of laws in aviation, this is about liability for an accident. This isn't any different than a Mexican registered bus travelling a road/city in Mexico that the US Government says is dangerous and asking if the Mexican travel company is liable, exactly the same with the word "airplane" replaced with "bus".

Yeah, I see your point, but I think you could rule out a lot more if you applied that rule.

Safe is a relative term.
The streets of Tehran are probably safe enough for most Iranians, but if you were an American in jeans and cowboy boots, sporting a red MAGA hat and wearing a US flag T-shirt it might be a different story.
Similarly a US flagged carrier could be at more risk than a regional Middle Eastern Airline.
The FAA does not dictate policy to the rest of the world and it would ultimately be up to a court of law to decide if there was negligence in the event of an incident leading to lawsuits.

Responsible is a vague term and airlines that operate from a given jurisdiction are not necessarily liable to comply with relations of another jurisdiction unless they enter it.
The most recent and fairly clear example of this was the recent groundings of the 737 Max series which did not all occur at the same time. After China grounded the FAA publicly reaffirmed the airworthiness of the aircraft although it ultimately grounded it not too long after.
Declaring an airspace as "unsafe" may also be more relevant to the country making the declaration than to aircraft from other countries. There is the potential for a fair bit of geo politics to play into all this.
In the reverse case under FAA regulations a PIC could be held responsible for entering a dangerous airspace they knew to be dangerous before the flight under FAA FAR 91.13 but that is a catch all and has some fairly wide latitude in terms of enforcement. Other countries may have similar regulations this varies by governing body.

Airlines from countries other than the USA aren't required to abide by US law when not operating inside the USA.
So an airline flying over Iran that isn't a US registered company isn't bound by FAA rules UNLESS their country of origin chooses to itself issue a regulation that copies that FAA rule (or a regulation that states that all FAA rules are to be complied with).
Many countries will generally follow the FAA when it comes to safety regulations and sometimes other things, but that often takes some time and is far from universal.
And of course in the shooting down of a Ukrainian airliner over Iran it was an aircraft on a direct flight between Iran and Ukraine, an airline that was probably in Iran at the time the FAA decided to ban overflight for US owned aircraft.


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Is there a daily list of diversions?
Is there a way to find a daily list of commercial flight diversions that have occurred?  If not, is there any way to compile one from available data?  Extra points if you can also get the reason.

No. Diversions can happen for all sorts of reasons, and often on very short notice. Info about diversions is not communicated and compiled systematically. Generally speaking, only the crew, ATC, airline, original destination and actual destination airport will know, none of which have any interest in publishing the data.

True, however (albeit off-topic on this site) one could attempt to compile such a list from publicly available sources (eg some flight-tracking sites show "diverted" status as it is pretty easy for them to detect that the actual landing airport is not the published destination for said flight #), so that is not a strict, definite "No"

@DeepSpace That would never be a complete list as such services do not have perfect coverage. They also don't necessarily know the intended destination of a flight. The same flight number does not always go to the same airport. This is especially true for cargo flights, where the destination sometimes changes very shortly before departure.

FlightAware in the USA for example has access to some limited information directly from the FAA. For filed IFR flights they know the intended departure and arrival airports and will even receive route updates in near-real time if the flight's route is amended in the ATC system.

I'm pretty sure the passengers will know. ;)


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Cessna 152 rattling/clanking noise in tail?
Going on a flight in a c152. Upon taxiing we hear a relatively loud and noticeable clanking/banging noise from what sounds like the tail. Never heard it before till this flight. Upon takeoff the noise gets more profound. Almost sounded as if the fuel cap wasn’t secure and the metal was banging. We requested to come back and land and upon inspection on the ground I could not find any external issues. I am unsure what this noise could be but it most definitely sounded like something broke off and was banging around somewhere in the tail section of the aircraft. It is a training aircraft so of course it gets a lot of wear and tear on it but I am unable to diagnose the issue. Lose bolt? Lose cable? Note that there were no issues with the integrity of the flight controls. Any help/ideas would be appreciated.

My idea is to have an A&P inspect it.

Did you perform a pre-flight inspection?

When this has happened to me it was a belt hanging out the door and the clasp banging against the side - but as it sounds like there were two of you onboard and I doubt one of you didnt have a belt on I doubt this is the answer.

Was the banging noise due to movement, or did you hear it when stationary? Did it change when you throttled up or down?

Noise was only prominent when aircraft was moving.

You are clearly not an aircraft mechanic. Stop operating the aircraft and take it to someone who is, have that person investigate and correct the issue. I am astonished you actually took off while hearing that noise coming from the tail.

@Jamiec I have also had it happen with a backpack strap that was hanging a few inches out of the door. It made quite a noise for a few minutes before I realized and pulled the backpack in.


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Do you have to repeat back ATC taxi instructions while still on the runway
Upon touching down while still rolling, tower gives us taxi instructions back to parking. I understand the need to give instructions on where to exit the runway  but I’m wondering if the FULL taxi instructions must be read back or only the taxi way we are exiting on is necessary. I find it difficult for student pilots to be landing an aircraft and focused on maintaining aircraft control while tower is giving them a long read back taxi clearance that warrants head down activity while still on the active runway. Is it “legal” to wait till clearing the runway and receiving those same instructions from ground when the aircraft at a full stop? For example tower will say “right on Foxtrot taxi to parking via DSE CROSS RWY 5” Is repeating back “right on Foxtrot” permitted? Thank you.

As soon as you're able—meaning once you've slowed to taxi speed, at the very latest—you should read back the runway exit instruction. Technically you don't have to read that back, you just have to perform the action, assuming of course that it's a reasonable place for you to exit. But if you don't read it back the controller will be in your ear giving the instruction again to make sure you heard it.
It's great if you can comprehend and read back a long taxi instruction like that, but it's understandable if you can't—especially for student pilots. SO if all you got was the exit point, you can read that back on its own, or you can toss in a little extra verbiage:

Right on Foxtrot and say again the rest, N345.

Right on Foxtrot, standby, N345.

Something like that is perfectly understandable and common, even for professional airline pilots. The important thing is to get off the runway without dawdling; everything else can wait a second or three.


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Question about V25 route's MOCA
I found something curious about the V25 route on the en-route low altitude chart. Before LAPED, there was no MOCA indicated, only an MEA of 9000. Why does MOCA 6500 appear after LAPED?

Terrain. It's easier to see if you look on the VFR chart instead. Heading southbound on V25, there is terrain up to about 7000 feet on V25 before LAPED. After LAPED, the highest terrain is only 4300 feet, so the MOCA can drop.

On the other hand, the VOR signal from RBL is blocked by that high terrain at lower altitudes. The farther past the high terrain you are, the higher you need to be to receive the VOR signal, which determines the MEA.


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Question about MOCA and MEA
Why is there sometimes a MOCA on the chart and sometimes only an MEA?
In the picture, there's only an MEA until BAGBY, and then MOCA appears after BAGBY. Do you know why this is happening?

Per the FAA defintion of MOCA, the service volume is limited to a 22 NM radius around a VOR.  So while it is possible to fly safely at 6,600 ft and navigate using GPS signals, pilots must use 8,500 ft minimum when navigating by VOR signals.
For those airways where MOCA is omitted, it is effectively equal to the MEA.
References:

FAA-H-8083-16B Instrument Procedures Handbook
FAA PCG Pilot/Controller Glossary
14 CFR § 91.177 Minimum altitudes for IFR operations.
14 CFR § 95 IFR Altitudes


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optimal loiter speed for an eVTOL air taxi
I'm not looking for a precise answer here, just a ballpark estimate of the optimal loiter speed for any model of eVTOL air taxi aircraft. In other words, if you just want to delay (kill time) in the air using the least amount of energy, what is a good airspeed range to fly? I'll take an answer for any eVTOL aircraft type that you know about. If you know the optimal cruise speed, I'd like to know that also. Thanks.

The answer is going to vary tremendously with the type of eVTOL.  For something that is basically just an overgrown quadcopter, with small-diameter fans/rotors, and no wing, the answer is probably zero airspeed.  Yet that would not be the case for an actual conventional helicopter (see https://www.spinningwing.com/the-helicopter/helicopter-performance#:~:text=This%20requires%20the%20helicopter%20to%20fly%20at,is%20the%20airspeed%20with%20the%20lowest%20fuel), nor for any craft with a fixed wing.  So-- I'd say that as asked, the question is so broad as to be basically unanswerable.

I would be very surprised if the optimal loiter speed for a quadcopter is zero. If it were zero for a quadcopter, why wouldn't it be zero for any rotorcraft, including helicopters? The link you provided for helicopters is interesting. As for my question being "unanswerable", why would that be? I said I'd take an answer for any eVTOL air taxi type that anyone here might know about. Just because you don't know the answer, that does not make it "unanswerable".

The optimal speed to kill time is zero -- zero airspeed, at zero altitude, with zero RPM.  Any scenario where "eVTOL air taxi aircraft" are flying around should have ample landing spaces where they can do that. Otherwise, "most efficient" still means discharging their battery at some fairly high rate, just not quite as high as it might be otherwise.

@user36086 do you have a link or a paper about this beaming recharging technology? I've never heard about it and it sounds interesting. Thanks in advance

https://ieeexplore.ieee.org/abstract/document/10311170

What you are looking for is the speed for minimum power required.
The fundamental difference between types of eVTOL aircraft for this question is whether this particular eVTOL has wings or not.
If it has wings, you will want to be fully transitioned to 'on-wing' flight and have the lifting propulsors in cruise mode.  You then want to fly at the minimum power required speed for the aircraft.
If it does not have wings (helicopter, quadcoper, etc).  You still want to fly with some forward velocity -- as rotorcraft (even helicopters) fly forward more efficiently than they hover.
To put numbers to this, you will need to build a drag / power model for the aircraft.  Search for power required.


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Meaning of “G” in aviation
The Singapore Ministry of Transport just published the preliminary report for SQ flight 321 yesterday (https://www.mot.gov.sg/news/details/transport-safety-investigation-bureau-preliminary-investigation-findings-of-incident-involving-sq321).
My question is about statement 3(a). It stated that -

The Gravitational force (G), recorded as vertical accelerations, fluctuated between positive (+ve) 0.44G and +ve 1.57G for a period of about 19 sec. (This would have caused the flight to begin to experience slight vibration)

Not an aviation expert here but in more layman understanding, vertically an aircraft could only be affected by either gravitational force or lift. And gravitational force, according to Newton’s law of universal gravitation (or Einstein’s general relativity if you prefer), should not change as long as the mass of the aircraft and the Earth do not change.
So it confuses me so much when the statement wrote that “gravitational force changes” (and this is reported by many news outlets).
Again, I’m not an aviation expert so here is my question: what IS the meaning of G in aviation? Or is there anything wrong with my understanding? Thank you.

From review: Does this answer your question? What is a "rapid changes in gravitational force"

G is a dimensionless ratio based upon the acceleration of an object divided by the acceleration that same object experiences in an earth-normal gravity field.  This is equal to 9.81 m/s^2 or 32.2 ft/s^2.
A person standing on Earth is subject to an acceleration of 9.81 m/s^2 due to the force of gravity.  That person is said to be in a 9.81/9.81 = 1G.  A pilot flying a military fighter in a hard turn to the left may experience an acceleration as high as 100 m/s^2 towards the outside of the turn.  This works out to be 100/9.81 = 10.2 G.
G ‘forces’ are also equivalent to the aircraft load factor at any given time.  Load factor is the ratio of the lift force created by the wings divided by the weight of the aircraft.  A light airplane weighing 2500 pounds and whose wings produce 10,000 pounds of lift at a given time is also subject to 4 G, since the 10000 lbs of lift divided by the 2500 lb gross weight also equal to 4.  Consequently, the airplane experiences an acceleration in the direction of the lift vector equal to 4 * 9.81 m/s^2 = 39.24 m/s^2.
In the case cited above, the aircraft is subject to aerodynamic loads, resulting in an acceleration upon the airframe which varied between +4.32 m/s^2 and -15.40 m/s^2, resulting in the cited +0.44/-1.57 G range.  The Singapore Ministry of Transport is not quite accurate in calling Gs The gravitational force.   As you correctly pointed out the gravitational force across the Earth is, for all intents and purposes here, constant.  But the loads and accelerations experienced by a person in flight from a certain reference point will vary due to the net forces acting upon their body.

When we use the term g's, we don't mean that gravity is actually changing.  Instead, we're normalizing the acceleration we feel by something we're familiar with -- i.e. the acceleration due to gravity.
When we're sitting statically in a chair, we feel 1g.  Gravity is pulling us down, the chair is pushing back up, we aren't accelerating either way.  This is normal.
Think about a time when you've felt significant vertical acceleration.  When a car or a roller coaster crests the top of a hill -- or rounds the bottom of a valley.  Or when a high speed elevator starts to drop from the top floor, or comes to a stop at the bottom.
In these situations, you feel either lighter or heavier.  Gravity is still pulling down the same, but the forces on you are not in equilibrium.  Either the chair or the floor below you is pushing up harder than your weight -- or it is pushing up less.  Because the forces are not in equilibrium, you are accelerating.  Or alternatively, because the chair (and car, roller coaster, or elevator around it) are accelerating, there is an imbalance of forces.
If you were in total free-fall (say you had jumped off a high dive, bungee jumping, or went sky diving) before the air resistance (or rubber band) slows you down, there are no forces pushing back up and you accelerate at the full acceleration due to gravity 9.8 $m/s^2$.  We call this feeling zero g's.  It is what astronauts feel all the time.
In fact, gravity is still present for astronauts in space.  Gravity is what keeps the spacecraft in orbit.  The spacecraft is in a freefall -- like the moment you step off a bungee jump.  But it is also moving 'around' the earth at a fast enough rate to exactly counter act the freefall.  They move forward with great speed and gravity pulls them inward to the earth -- together they maintain a circular path called an orbit.  This state of constant freefall means they feel weightless (zero g's) the whole time.
Back to our people in an airplane.  Instead of a nice smooth ride, they are basically riding a rough roller coaster with bumps up and down.  When they reach the peaks and must accelerate down, they feel less than one g like when the elevator starts to go down.  When they reach a valley and must accelerate back up, they feel more than one g like the roller coaster curving back up.
This oscillation can happen slow or fast -- slow and it might only feel like rocking of waves.  Fast and it will feel like driving on a rough dirt road with no suspension.


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Is there a tool to learn to pronounce aviation jargon accurately?
So I've been reading technical aviation books and I come across a lot words I want to learn to say correctly but unlike simple words which I just look up in an audio Oxford dictionary I can't think of where online I can find audio pronunciations of aviation words. Any suggestions?

Would you mind perhaps giving some examples? :)

@MikeFoxtrot Like...DIHEDRAL.  ☺

I don't think you will find a specific aviation resource but most words should be in online dictionaries, for example, dihedral.  Click Syllables then the speaker to hear it.

With the exception of abbreviations (like FSDO, pronounced fizz dough) there's not much "jargon" in aviation that's not a standard word in whatever language you're speaking. Words like "dihedral", "anhedral", "aileron", etc. should certainly show up in a dictionary.
The abbreviations are "tribal knowledge" the same way they are in any other field (e.g. SCSI, SATA, IMAP in the tech field). I'm not aware of any authoritative compendium of pronunciations.

There probably isn't a reference, per se, but you can hear a lot of these words in context a few of ways:

http://www.liveatc.net - Is one great example.  It will allow you to listen to live ATC, and they'll be saying a lot of the same world you want to hear.
https://www.pilotedge.net - Along the same lines, but instead it's a plugin for your flight simulator that allows you to interact with actual ATC professionals on a virtual ATC network.  Not only good for listening, but also for learning to use a lot of the words.
http://www.youtube.com - Okay, this probably didn't need to be listed like this, but it's also useful :).  There are A LOT of videos online for learning aviation, and they probably use many of the words you are curious about.  So I'd try that as well.

Between all these resources it should be pretty easy to get at the "tribal knowledge" voretaq7 referenced in his answer.

Well, damn, memories are bittersweet. I went to liveatc.net, saw that they had an Android app, downloaded it, and brought up KJFK tower ... and then cried a little. I retired nearly 16 years ago now, but I still severely miss flying. I was based at KJFK for the last 10 years.


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What exactly is the purpose of a pilot keeping a logbook?
More specifically: in Canada what are reasons and protocols of keeping a logbook?

Almost everything in flying is measured in hours, including your experience.
To start with, in most places you need to have trained a certain number of hours before taking your flying skills test, regardless of how good you are.
And then it continues, want to do an instrument rating, you need x hours. Want to be an instructor, you need y hours. Want to be a Captain on a 747, well you'll need z hours as First Officer first and to be First Officer, you'll need....guess what!
Beyond that, many countries place restrictions on what you can and can't do based on your recent experience. For example, in the UK, to take passengers you must have performed three landings on type within 90 days.
And then it carries on outside of legislation, too - if you want to rent a plane most places will place some sort of hour requirement, whether it be your total hours or hours on type etc.
And so it follows that you need somewhere to log this. As a pilot your log book is sacrosanct - its a legal document forming a factual record of your flying experience.

What if people record inaccurate hours to reach their goal faster? How is that checked?

@verve It's mostly not, from what I gather. Some things will need signing off as true by an instructor, but if you fake hours then you do so knowing that if you ever do have an incident then you stand a chance of having your whole history audited. You may get away with padding hours flying around in a radio less microlight, but padding your big jet time leaves a big trail.

How do some pilots manage without keeping a logbook if it's so important?

@verve I can't imagine many qualified pilots not keeping a logbook.

I read some super-pros don't keep logbooks but some other records. Forgot where...

@verve if you are employed by a part 121 carrier and you do no outside flying then you can prove currency from company records alone.  If you ever want to move to a different company though, better keep up with the logbook.

Just to throw it in here: I got to known a former airline pilot who is now only flying for fun. He has stopped logging his hours after he quit flying for an airline, and is only logging his biennial flight review (as required by law). He simply doesn't need the experience or the ours to fly the plane he rents as they know him well.